Power supply device, electronic device, control method, and recording medium

ABSTRACT

A power supply device includes a power supply unit that wirelessly supplies power, a communication unit that communicates with an electronic device, and a control unit that controls the communication unit to transmit a predetermined data to the electronic device based on whether or not the electronic device is connected to an external device supplying power to the electronic device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation, and claims the benefit, of U.S.patent application Ser. No. 13/753,345 filed Jan. 29, 2013, which claimsthe benefit of Japanese Patent Application No. 2012-020012 filed Feb. 1,2012. Each of U.S. patent application Ser. No. 13/753,345 and JapanesePatent Application No. 2012-020012 is hereby incorporated by referenceherein in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a power supply device for wirelesslysupplying the power, a control method, an electronic device, and arecording medium

Description of the Related Art

In recent years, there has been a power supply system which is known toinclude a battery charger having a primary coil for wirelesslyoutputting the power without connector connection, and a mobile phonehaving a secondary coil for wirelessly receiving the power supplied fromthe battery charger.

Japanese Patent Application Laid-Open No. 2008-67532 discusses a mobilephone with which the power is supplied from an alternating current (AC)adapter when it is connected with the AC adapter or from a batterycharger when it is inserted into the battery charger.

Conventionally, which of the AC adapter and the battery charger themobile phone should receive the power from has not been taken intoconsideration in a case where the mobile phone is connected with the ACadapter and inserted into the battery charger.

There has been a case where excessive power is supplied to the mobilephone if the mobile phone receives the power from the AC adapter and thebattery charger. To prevent such a situation, it has been necessary toselect an apparatus capable of supplying suitable power to a mobilephone and then supply the power to the mobile phone with the selectedapparatus.

The present invention relates to a technique for selecting an apparatuscapable of supplying suitable power to an electronic device.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided apower supply device including a power supply unit that wirelesslysupplies power, a communication unit that communicates with anelectronic device, and a control unit that controls the communicationunit to transmit predetermined data to the electronic device based onwhether or not the electronic device and an external device areconnected, wherein the predetermined data includes one of first data anda second data, the first data is used for causing the electronic deviceto receive power from the external device, and the second data is usedfor causing the electronic device to receive power from the power supplydevice, and wherein the external device includes a device for supplyingpower to the electronic device.

According to another aspect of the present invention, there is providedan electronic device including a connection unit that connects to anexternal device, a power receiving unit that wirelessly receives powerfrom a power supply device, a communication unit that communicates withthe power supply device, and a control unit that controls thecommunication unit so as to transmit predetermined information to thepower supply device, wherein the predetermined information indicateswhether or not the connection unit and the external device areconnected, and wherein the external device includes a device forsupplying power to the electronic device via the connection unit.

According to yet another aspect of the present invention, there isprovided a method for controlling a power supply device includingwirelessly supplying power, communicating with an electronic device, andtransmitting predetermined data to the electronic device based onwhether or not the electronic device and an external device areconnected, wherein the predetermined data includes one of first data anda second data, the first data is used for causing the electronic deviceto receive power from the external device, and the second data is usedfor causing the electronic device to receive power from the power supplydevice, and wherein the external device includes a device for supplyingpower to the electronic device.

According to yet another aspect of the present invention, there isprovided a method for controlling an electronic device including aconnection unit that connects to an external device. The methodincluding wirelessly receiving power, communicating with a power supplydevice, and transmitting predetermined information to the power supplydevice, wherein the predetermined information indicates whether or not aconnection unit and an external device are connected, and wherein theexternal device includes an device for supplying power to the electronicdevice via the connection unit.

According to yet another aspect of the present invention, there isprovided a recording medium recording a program for causing a computerto execute a method for controlling a power supply device. The methodincludes wirelessly supplying power, communicating with an electronicdevice; and transmitting predetermined data to the electronic devicebased on whether or not the electronic device and an external device areconnected, wherein the predetermined data includes one of first data anda second data, the first data is used for causing the electronic deviceto receive power from the external device, and the second data is usedfor causing the electronic device to receive power from the power supplydevice, and wherein the external device includes a device for supplyingpower to the electronic device.

According to yet another aspect of the present invention, there isprovided a recording medium recording a program for causing a computerto execute a method for controlling an electronic device including aconnection unit that connects to an external device. The method includeswirelessly receiving power, communicating with a power supply device,and transmitting predetermined information to the power supply device,wherein the predetermined information indicates whether or not theconnection unit and an external device are connected, and wherein theexternal device includes a device for supplying power to the electronicdevice via the connection unit.

Further features and aspects of the present invention will becomeapparent from the following detailed description of exemplaryembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate exemplary embodiments, features,and aspects of the invention and, together with the description, serveto explain the principles of the invention.

FIG. 1 illustrates an example of a power supply system according to afirst exemplary embodiment.

FIG. 2 (including FIGS. 2A and 2B) is an example of a block diagramillustrating the power supply system according to the first exemplaryembodiment.

FIG. 3 illustrates an example of a configuration of a first switchingunit of an electronic device according to the first exemplaryembodiment.

FIG. 4 is a flowchart illustrating an example of a selection processperformed by a power supply apparatus according to the first exemplaryembodiment.

FIG. 5 is a flowchart illustrating an example of a selection processperformed by a power supply apparatus according to a second exemplaryembodiment.

FIG. 6 is a flowchart illustrating an example of an exception processperformed by the power supply apparatus according to the secondexemplary embodiment.

FIG. 7 illustrates an example of a power supply system according to thesecond exemplary embodiment.

FIG. 8 illustrates an example of a configuration of a first switchingunit of an electronic device according to a third exemplary embodiment.

DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the inventionwill be described in detail below with reference to the drawings.

A first exemplary embodiment of the present invention will be describedin detail below with reference to the accompanying drawings. A powersupply system according to the first exemplary embodiment includes apower supply apparatus 100 and an electronic device 200, as illustratedin FIG. 1.

With the power supply system according to the first exemplaryembodiment, when the power supply apparatus 100 and the electronicdevice 200 exist within a predetermined range, the power supplyapparatus 100 wirelessly supplies the power to the electronic device200. When the power supply apparatus 100 and the electronic device 200exist within the predetermined range, the electronic device 200wirelessly receives the power output from the power supply apparatus100. When the power supply apparatus 100 and the electronic device 200do not exist within the predetermined range, the electronic device 200cannot receive the power from the power supply apparatus 100. Thepredetermined range is also a range within which the power supplyapparatus 100 and the electronic device 200 can communicate with eachother. The power supply apparatus 100 can also wirelessly supply thepower in parallel to a plurality of electronic devices.

The electronic device 200 illustrated in FIG. 1 is supplied from anexternal apparatus 400 via a cable 300. In this case, the electronicdevice 200 is supplied power by wireless from the power supply apparatus100. The first exemplary embodiment will be described below on thepremise that the cable 300 is a predetermined interface conforming tothe Universal Serial Bus (USB) standard.

The electronic devices 200 may be an imaging apparatus such as a camera,or a reproducing apparatus for reproducing audio and video data. Theelectronic device 200 may be a mobile device such as a mobile phone orsmart phone. The electronic device 200 may also be a battery packincluding a battery 211.

The electronic device 200 may also be a car-like apparatus which isdriven by the power supplied from the power supply apparatus 100. Theelectronic device 200 may also be an apparatus for receiving televisionbroadcasting, a display for displaying video data, or a personalcomputer. The electronic device 200 may bean apparatus which operates onthe power supplied from the power supply apparatus 100 even if thebattery 211 is not attached to the electronic device 200.

The external apparatus 400 is to be, for example, a personal computer ora television.

FIG. 2 (including FIGS. 2A and 2B) is a block diagram illustrating thepower supply system according to the first exemplary embodiment. Thepower supply apparatus 100 includes a conversion unit 101, an oscillator102, a power generation unit 103, a matching circuit 104, a modulationand demodulation circuit 105, a power transmitting antenna 106, acentral processing unit (CPU) 107, a read-only memory (ROM) 108, arandom access memory (RAM) 109, a display unit 110, an operation unit111, and a reflected power detection circuit 112, as illustrated in FIG.2.

When an AC power source (not illustrated) and the power supply apparatus100 are connected, the conversion unit 101 converts the AC powersupplied from the AC power source (not illustrated) into the directcurrent (DC) power and then supplies the converted DC power to the powersupply apparatus 100.

The oscillator 102 oscillates a frequency to be used to control thepower generation unit 103 to convert the power supplied from theconversion unit 101 into the power corresponding to a target value setby the CPU 107. The oscillator 102 may be, for example, a crystalresonator.

Based on the power supplied from the conversion unit 101 and thefrequency oscillated by the oscillator 102, the power generation unit103 generates the power to be output to the outside via the powertransmitting antenna 106. The power generation unit 103 includes a fieldeffect transistor (FET) and controls a current flowing between sourceand drain terminals of the FET according to the frequency oscillated bythe oscillator 102 to generate the power to be output to the outside.The power generated by the power generation unit 103 is supplied to thematching circuit 104 via the reflected power detection circuit 112. Thepower generated by the power generation unit 103 includes first powerand second power.

The first power is supplied to the electronic device 200 to enable thepower supply apparatus 100 to perform wireless communication with theelectronic device 200. The second power is supplied to the electronicdevice 200 when the power supply apparatus 100 supplies the power to theelectronic device 200. For example, the first power is 1 W or less andthe second power is 2 W to 10 W. The second power may be 10 W or higher.The first power is to be lower than the second power. The first power isnot limited to the power equal to or less than 1 W as long as it is usedby the power supply apparatus 100 to perform wireless communication.

When the power supply apparatus 100 is supplying the first power to theelectronic device 200, the power supply apparatus 100 can performwireless communication conforming to the Near Field Communication (NFC)standard with the electronic device 200 via the power transmittingantenna 106. However, when the power supply apparatus 100 is supplyingthe second power to the electronic device 200, the power supplyapparatus 100 cannot perform wireless communication conforming to theNFC standard with the electronic device 200 via the power transmittingantenna 106.

The matching circuit 104 is a resonance circuit for causing a resonancebetween the power transmitting antenna 106 and a power receiving antennaincluded in an apparatus corresponding to the power supply apparatus100, according to the frequency oscillated by the oscillator 102. Thematching circuit 104 is also a circuit for performing impedance matchingbetween the power generation unit 103 and the power transmitting antenna106. The matching circuit 104 includes a capacitor, a coil, a resistor,and so on. The CPU 107 can control a resonant frequency f of the powersupply apparatus 100 by controlling the capacitor and coil included inthe matching circuit 104. The resonant frequency f is used to cause aresonance between the power supply apparatus 100 and an apparatussubjected to power supply from the power supply apparatus 100.

The resonant frequency f is represented by the following formula (1),where L indicates the inductance of the matching circuit 104, and Cindicates the capacitance of the matching circuit 104.

$\; \begin{matrix}\left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack & \; \\{f = \frac{1}{2\; \pi \sqrt{LC}}} & (1)\end{matrix}$

The resonant frequency f may be a commercial frequency (50/60 Hz), 10 toseveral tens MHz, or 13.56 MHz. The resonant frequency f may also be6.78 MHz.

The matching circuit 104 can also detect a change of the current flowingto the power transmitting antenna 106. The matching circuit 104 can alsodetect a change of the voltage supplied to the power transmittingantenna 106.

In a state where the frequency oscillated by the oscillator 102 is setto the resonant frequency f, the power generated by the power generationunit 103 is supplied to the power transmitting antenna 106 via thematching circuit 104.

The modulation and demodulation circuit 105 is used for performingwireless communication conforming to the NFC standard between the powersupply apparatus 100 and the electronic device 200. When the powersupply apparatus 100 transmits to the electronic device 200 control data(hereinafter referred to as a command) for controlling the electronicdevice 200, the modulation and demodulation circuit 105 modulates thepower generated by the power generation unit 103 based on a protocolconforming to the NFC standard.

The modulation and demodulation circuit 105 converts the power generatedby the power generation unit 103 into a pulse signal through theamplitude shift keying (ASK) modulation utilizing the amplitudedisplacement. The pulse signal converted as a command is transmitted tothe electronic device 200 via the power transmitting antenna 106. Whenthe pulse signal is transmitted to the electronic device 200, theelectronic device 200 analyzes the pulse signal to detect bit datacontaining information “1” and “0”. The ASK modulation is a modulationmethod utilizing the amplitude displacement, and is used forcommunication between an integrated circuit (IC) card and a card reader.

The modulation and demodulation circuit 105 further includes a codingcircuit conforming to a predetermined coding method.

According to a change of the current flowing to the power transmittingantenna 106 detected by the matching circuit 104, the modulation anddemodulation circuit 105 can demodulate, through the coding circuit,response data from the electronic device 200 corresponding to a commandtransmitted to the electronic device 200 and control data from theelectronic device 200. Thus, based on a load modulation method, themodulation and demodulation circuit 105 can receive from the electronicdevice 200 the response data corresponding to a command transmitted tothe electronic device 200 and the control data transmitted from theelectronic device 200.

The modulation and demodulation circuit 105 transmits a command to theelectronic device 200 in response to an instruction from the CPU 107.Upon reception of the response data and the control data from theelectronic device 200, the modulation and demodulation circuit 105demodulates the received response data and the control data and thensupplies the data to the CPU 107.

The power transmitting antenna 106 is used for outputting to the outsidethe power generated by the power generation unit 103. The power supplyapparatus 100 supplies the power to the electronic device 200 via thepower transmitting antenna 106. The power supply apparatus 100 transmitsa command to the electronic device 200 via the power transmittingantenna 106. In addition, the power supply apparatus 100 receives fromthe electronic device 200 via the power transmitting antenna 106 thecontrol data and the response data corresponding to a commandtransmitted to the electronic device 200.

The CPU (Central Processing Unit) 107 executes a computer program storedin the ROM 108 to control the power supply apparatus 100. The CPU 107controls the power generation unit 103 to control the power forsupplying wirelessly to the electronic device 200.

The ROM 108 stores a computer program for controlling the power supplyapparatus 100 and information such as parameters related to the powersupply apparatus 100. The RAM 109 which is a rewritable memory records acomputer program for controlling the power supply apparatus 100,information such as parameters related to the power supply apparatus100, and data received from the electronic device 200 by the modulationand demodulation circuit 105.

The display unit 110 displays either video data supplied from the RAM109 or video data supplied from the ROM 108.

The operation unit 111 provides a user interface for operating the powersupply apparatus 100. The operation unit 111 includes a power button ofthe power supply apparatus 100 and a mode switching button of the powersupply apparatus 100. Each button is formed of a switch, a touch panel,or the like. The CPU 107 controls the power supply apparatus 100according to a user instruction input via the operation unit 111.

The reflected power detection circuit 112 detects information indicatingan amplitude voltage V1 of a traveling wave of the power output by thepower transmitting antenna 106. The reflected power detection circuit112 detects information indicating an amplitude voltage V2 of areflected wave of the power output by the power transmitting antenna106. The information indicating the amplitude voltage V1 and theinformation indicating the amplitude voltage V2 detected by thereflected power detection circuit 112 are supplied to the CPU 107. TheCPU 107 records in the RAM 109 the information indicating the amplitudevoltage V1 and the information indicating the amplitude voltage V2supplied from the reflected power detection circuit 112.

The CPU 107 obtains a voltage reflection coefficient ρ based on theamplitude voltage V1 of the traveling wave and the amplitude voltage V2of the reflected wave. In addition, the CPU 107 calculates a voltagestanding wave ratio (VSWR) based on the voltage reflection coefficientρ.

The voltage standing wave ratio (VSWR) indicates a relation between thetraveling wave of the power output from the power transmitting antenna106 and the reflected wave of the power output from the powertransmitting antenna 106. A value of the voltage standing wave ratio(VSWR) closer to 1 indicates lower reflected power, a smaller loss ofthe power supplied from the power supply apparatus 100 to an externalelectronic device, and higher power transmission efficiency.

The following formula (2) represents the voltage reflection coefficientρ.

$\; \begin{matrix}\left\lbrack {{Formula}\mspace{14mu} 2} \right\rbrack & \; \\{\rho = \frac{V\; 2}{V\; 1}} & (2)\end{matrix}$

The following formula (3) represents the voltage standing wave ratioVSWR.

$\begin{matrix}\left\lbrack {{Formula}\mspace{14mu} 3} \right\rbrack & \; \\{{VSWR} = \frac{1 + \rho}{1 - \rho}} & (3)\end{matrix}$

Hereinbelow, the voltage standing wave ratio VSWR is referred to as“VSWR”.

Based on the calculated VSWR, the CPU 107 determines whether theelectronic device 200 is placed in the vicinity of the power supplyapparatus 100.

An example of a configuration of the electronic device 200 will bedescribed below with reference to FIG. 2. The electronic device 200includes a power receiving antenna 201, a matching circuit 202, arectifying and smoothing circuit 203, a modulation and demodulationcircuit 204, a CPU 205, a ROM 206, a RAM 207, a current and voltagedetection unit 208, a regulator 209, a charging control unit 210, and abattery 211. The electronic device 200 further includes a firstswitching unit 212, a connector 213, a detection unit 214, a currentlimiting unit 215, a second switching unit 216, and a communication unit217.

The power receiving antenna 201 is used for receiving the power suppliedfrom the power supply apparatus 100. The electronic device 200 receivesthe power from the power supply apparatus 100 via the power receivingantenna 201. The electronic device 200 performs communication conformingto the NFC standard with the power supply apparatus 100 via the powerreceiving antenna 201. Upon reception of a command from the power supplyapparatus 100 via the power receiving antenna 201, the electronic device200 transmits to the power supply apparatus 100 via the power receivingantenna 201 response data corresponding to the command received from thepower supply apparatus 100.

The matching circuit 202 is a resonance circuit for performing impedancematching so that the power receiving antenna 201 resonates with the samefrequency as the resonant frequency f of the power supply apparatus 100.Similar to the matching circuit 104, the matching circuit 202 includes acapacitor, a coil, a resistor, and so on. The matching circuit 202controls the matching circuit 202 so that the power receiving antenna201 resonates with the same frequency as the resonant frequency f of thepower supply apparatus 100. The matching circuit 202 supplies the powerreceived by the power receiving antenna 201 to the rectifying andsmoothing circuit 203.

The rectifying and smoothing circuit 203 removes a command and noisefrom the power received by the power receiving antenna 201 to generateDC power. The rectifying and smoothing circuit 203 further supplies thegenerated DC power to the regulator 209 via the current and voltagedetection unit 208 and the first switching unit 212. The rectifying andsmoothing circuit 203 supplies to the modulation and demodulationcircuit 204 the command removed from the power received by the powerreceiving antenna 201.

The modulation and demodulation circuit 204 analyzes the commandsupplied from the rectifying and smoothing circuit 203 according to acommunication protocol corresponding to the power supply apparatus 100and then supplies a result of the command analysis to the CPU 205. Whenthe power supply apparatus 100 is supplying the first power to theelectronic device 200, the CPU 205 controls the modulation anddemodulation circuit 204 so that the load included in the modulation anddemodulation circuit 204 is fluctuated to transmit to the power supplyapparatus 100 the response data corresponding to the command. Variationin the load included in the modulation and demodulation circuit 204causes a change of the current flowing to the power transmitting antenna106. Thus, the power supply apparatus 100 detects a change of thecurrent flowing to the power transmitting antenna 106 so as to receivethe response data corresponding to the command transmitted from theelectronic device 200.

The CPU 205 determines what type of command that the command received bythe modulation and demodulation circuit 204 is based on the result ofthe analysis supplied from the modulation and demodulation circuit 204.The CPU 205 then controls the electronic device 200 to perform a processand an operation specified by a command code corresponding to thereceived command. The CPU 205 executes a computer program stored in theROM 206 to control the electronic device 200.

The ROM 206 stores a computer program for controlling the electronicdevice 200. Information about the electronic device 200 is recorded inthe ROM 206. The RAM 207 which is a rewritable memory records thecomputer program for controlling the electronic device 200 and datatransmitted from the power supply apparatus 100.

The current and voltage detection unit 208 detects the voltage of thepower supplied from the rectifying and smoothing circuit 203. Further,the current and voltage detection unit 208 detects the current of thepower supplied from the rectifying and smoothing circuit 203. Thecurrent and voltage detection unit 208 supplies current informationindicating the detected current and voltage information indicating thedetected voltage to the CPU 205.

In response to an instruction from the CPU 205, the regulator 209performs control to supply to the electronic device 200 any one of thepower supplied from the rectifying and smoothing circuit 203, the powersupplied from the battery 211, and the power supplied from the externalapparatus 400 via the cable 300. When the battery 211 is being chargedin the electronic device 200, the regulator 209 supplies to theelectronic device 200 either the power supplied from the rectifying andsmoothing circuit 203 or the power supplied from the external apparatus400 via the cable 300.

When the power is supplied from the regulator 209, the charging controlunit 210 controls charging of the battery 211. The battery 211 isdetachably attached to the electronic device 200. The battery 211 is arechargeable secondary battery, for example, a lithium ion battery. Thebattery 211 may be a battery other than a lithium ion battery.

The first switching unit 212 is used for supplying to the regulator 209either the power supplied from the rectifying and smoothing circuit 203or the power supplied from the external apparatus 400 via the cable 300.When the CPU 205 controls the first switching unit 212 so that the powersupplied from the rectifying and smoothing circuit 203 is supplied tothe regulator 209, the power supplied from the external apparatus 400via the cable 300 is not supplied to the regulator 209. When the CPU 205controls the first switching unit 212 so that the power supplied fromthe external apparatus 400 via the cable 300 is supplied to theregulator 209, the power supplied from the rectifying and smoothingcircuit 203 is not supplied to the regulator 209. The CPU 205 can alsocontrol the first switching unit 212 not to supply to the regulator 209the power supplied from the rectifying and smoothing circuit 203 and thepower supplied from the external apparatus 400 via the cable 300.

The connector 213 is a connection terminal for connecting the cable 300.The connector 213 is provided with a virtual bus (VBUS) terminal, aground (GND) terminal, a D+ terminal, and a D− terminal.

The detection unit 214 detects the potential of the D+ terminal and thepotential of the D-terminal so as to detect the type of the power sourceof the external apparatus 400.

Types of power source specified in the Battery Charging Specification inthe USB standard include a standard downstream port, a chargingdownstream port, and a dedicated charging port. The detection unit 214detects whether the external apparatus 400 conforms to any one of thestandard downstream port, the charging downstream port, and thededicated charging port.

The standard downstream port can supply maximum 500 mA current to theelectronic device 200. Hereinbelow, the standard downstream port isreferred to as “SDP”. The charging downstream port can supply maximum1500 mA current to the electronic device 200. The charging downstreamport is referred to as “CDP”. The dedicated charging port can supplymaximum 1500 mA current to the electronic device 200. The dedicatedcharging port is referred to as “DCP”.

When the type of the power source of the external apparatus 400 isdetected, the detection unit 214 notifies the CPU 205 of the type of thepower source corresponding to the external apparatus 400. According tothe USB standard applicable to the external apparatus 400, the detectionunit 214 may detect the type of the power source corresponding to theexternal apparatus 400 by detecting how much current the externalapparatus 400 can supply to the electronic device 200.

In a case where the connector 213 and the external apparatus 400 areconnected via the cable 300, when the type of the power sourcecorresponding to the external apparatus 400 is detected, the CPU 205sets a flag f to ON. The flag f is data which indicates that theelectronic device 200 can receive the power from the external apparatus400. The flag f is recorded in the RAM 207. In a case where theconnector 213 and the external apparatus 400 are not connected via thecable 300, the CPU 205 sets the flag f to OFF. In a case where theconnector 213 and the external apparatus 400 are connected via the cable300, when the type of the power source corresponding to the externalapparatus 400 is not detected, the CPU 205 sets the flag f to OFF.

For example, when the external apparatus 400 is detected not to conformto the SDP, the CDP, and the DCP, even if the connector 213 and theexternal apparatus 400 are connected via the cable 300, the CPU 205 setsthe flag f to OFF.

In a case where the external apparatus 400 and the connector 213 areconnected via the cable 300, the current limiting unit 215 limits thecurrent supplied from the VBUS terminal according to the type of thepower source detected by the detection unit 214. For example, when theexternal apparatus 400 conforms to the SDP, the current limiting unit215 performs control so that the current supplied from the VBUS terminalbecomes 500 mA or less. For example, when the external apparatus 400conforms to the CDP, the current limiting unit 215 performs control sothat the current supplied from the VBUS terminal becomes 1500 mA orless. According to the type of the power source of the externalapparatus 400, the current limiting unit 215 may perform control so thatthe current supplied from the VBUS terminal becomes 100 mA or less. Thecurrent controlled by the current limiting unit 215 is supplied to theregulator 209 via the first switching unit 212.

The second switching unit 216 is used for connecting the D+ andD-terminals of the connector 213 with either the communication unit 217or the detection unit 214. If the mode of the electronic device 200 iseither a mass storage device mode or an imaging device mode, the CPU 205can control the second switching unit 216 to connect the D+ and D−terminals of the connector 213 with the communication unit 217. When theD+ and D− terminals of the connector 213 and the communication unit 217are connected, the communication unit 217 can transmit data to theexternal apparatus 400 and receive data from the external apparatus 400via the cable 300. When the D+ and D− terminals of the connector 213 andthe communication unit 217 are connected, the D+ and D− terminals of theconnector 213 and the detection unit 214 are assumed to be unconnected.

When the mode of the electronic device 200 is a human interface device(HID) mode, the CPU 205 can control the second switching unit 216 so asnot to connect the D+ and D− terminals of the connector 213 and thecommunication unit 217. When the D+ and D− terminals of the connector213 and the communication unit 217 are not connected, the communicationunit 217 cannot transmit data to the external apparatus 400 or receivedata from the external apparatus 400 via the cable 300. When the D+ andD− terminals of the connector 213 and the communication unit 217 are notconnected, the D+ and D− terminals of the connector 213 and thedetection unit 214 are assumed to be connected.

The communication unit 217 transmits data to the external apparatus 400via the cable 300 and receives data supplied from the external apparatus400 via the cable 300.

FIG. 3 illustrates an example of a configuration of the first switchingunit 212. The first switching unit 212 includes a switch 501, a switch502, a diode 503, a diode 504, and a resistor 505.

Referring to FIG. 3, the rectifying and smoothing circuit 203 and theregulator 209 are connected via the diode 503 and the switch 501. Thecurrent limiting unit 215 and the regulator 209 are connected via thediode 504 and the switch 502.

The resistor 505 is connected between the diode 504 and the CPU 205.When the power is supplied from the external apparatus 400 to theelectronic device 200 via the connector 213, a voltage is generated atthe resistor 505. The CPU 205 can detect whether the power is suppliedfrom the external apparatus 400 by detecting the voltage of the resistor505.

The CPU 205 can select either the power supply apparatus 100 or theexternal apparatus 400 as an apparatus which supplies the power to theelectronic device 200 by controlling the switches 501 and 502. When theswitch 501 is turned ON and the switch 502 is turned OFF by the CPU 205,the power supply apparatus 100 is selected as an apparatus whichsupplies the power to the electronic device 200. When the switch 501 isturned OFF and the switch 502 is turned ON by the CPU 205, the externalapparatus 400 is selected as an apparatus which supplies the power tothe electronic device 200.

The power transmitting antenna 106 and the power receiving antenna 201may be a helical antenna, a loop antenna, or a planar antenna such as ameander line antenna.

In the first exemplary embodiment, the process performed by the powersupply apparatus 100 is also applicable to a system in which the powersupply apparatus 100 wirelessly supplies the power to the electronicdevice 200 through electromagnetic field coupling. Further, in the firstexemplary embodiment, the process performed by the power supplyapparatus 100 is also applicable to a system in which, when an electrodeis provided on the power supply apparatus 100 and an electrode isprovided on the electronic device 200, the power supply apparatus 100wirelessly supplies the power to the electronic device 200 throughelectric field coupling. Further, in the first exemplary embodiment, theprocess performed by the power supply apparatus 100 is also applicableto a system in which the power supply apparatus 100 wirelessly suppliesthe power to the electronic device 200 through electromagneticinduction.

Further, in the first exemplary embodiment, the power supply apparatus100 wirelessly outputs the power to the electronic device 200, and theelectronic device 200 wirelessly receives the power from the powersupply apparatus 100. However, the term “wireless” may be replaced by“non-contact” or “contactless”.

The electronic device 200 illustrated in FIG. 1 is supplies powerwirelessly from the power supply apparatus 100 and supplied from theexternal apparatus 400 via the cable 300. In such a case, the powersupply apparatus 100 needs to select either the power supply apparatus100 or the external apparatus 400 as an apparatus which supplies thepower to the electronic device 200. Therefore, the power supplyapparatus 100 performs a selection process for selecting an apparatuswhich supplies the power to the electronic device 200.

(Selection Process)

The selection process performed by the power supply apparatus 100according to the first exemplary embodiment will be described below withreference to the flowchart in FIG. 4. The selection process can beimplemented when the CPU 107 executes a computer program stored in theROM 108.

The CPU 107 controls the oscillator 102, the power generation unit 103,and the matching circuit 104 to output the first power via the powertransmitting antenna 106 so as to detect whether the electronic device200 exists within the predetermined range of distance. In this case, theCPU 107 monitors a change of the VSWR and, based on a change of theVSWR, detects whether the electronic device 200 exists within thepredetermined range.

In step S401, the CPU 107 detects whether the electronic device 200exists within the predetermined range. When a change of the VSWR isequal to or larger than a predetermined value A, the CPU 107 determinesthat the electronic device 200 is exists within the predetermined range.When a change of the VSWR is less than the predetermined value A, theCPU 107 determines that the electronic device 200 does not exist withinthe predetermined range. When the CPU 107 determines that the electronicdevice 200 exists within the predetermined range (YES in step S401), theprocess proceeds from step S401 to step S402. When the CPU 107determines that the electronic device 200 does not exist within thepredetermined range (NO in step S401), the process proceeds from stepS401 to step S405. The predetermined value A may be set so that the CPU107 can detect that at least one electronic device is placed in thevicinity of the power supply apparatus 100.

In step S402, the CPU 107 determines whether a plurality of electronicdevices exist within the predetermined range. For example, in a casewhere the electronic device 200 and an electronic device other than theelectronic device 200 exist within the predetermined range, the CPU 107determines that a plurality of electronic devices exist within thepredetermined range. When the CPU 107 determines that a plurality ofelectronic devices exists within the predetermined range of distance(YES in step S402), the process proceeds from step S402 to step S404.When the CPU 107 determines that a plurality of electronic devices doesnot exist within the predetermined range (NO in step S402), the CPU 107determines that one unit of the electronic device 200 exists within thepredetermined range. In this case (NO in step S402), the processproceeds from step S402 to step S403.

In step S403, the CPU 107 determines whether the electronic device 200is in a state enabling to receive the power from the external apparatus400.

The CPU 107 performs wireless communication conforming to the NFCstandard to transmit to the electronic device 200 a first command fordetermining whether the electronic device 200 can receives the powerfrom the external apparatus 400. Upon reception of the first commandfrom the power supply apparatus 100, the electronic device 200 detectswhether the flag f recorded in the RAM 207 is set to ON.

If the flag f recorded in the RAM 207 is set to ON, the electronicdevice 200 transmits to the power supply apparatus 100 response dataindicating that the electric device 200 is in a state enabling toreceive the power from the external apparatus 400. If the flag frecorded in the RAM 207 is set to OFF, the electronic device 200transmits to the power supply apparatus 100 response data indicatingthat the electric device 200 is not in a state enabling to receive thepower from the external apparatus 400. According to the response datacorresponding to the first command, the CPU 107 determines whether theelectronic device 200 is in a state enabling to receive the power fromthe external apparatus 400. The electronic device 200 can receive thepower from the external apparatus 400 if the electronic device 200 is ina state enabling to receive the power from the external apparatus 400.The electronic device 200 cannot receive the power from the externalapparatus 400 if the electronic device 200 is not in a state enabling toreceive the power from the external apparatus 400.

When the CPU 107 determines that the electronic device 200 is in a stateenabling to receive the power from the external apparatus 400 (YES instep S403), the process proceeds from step S403 to step S404. When theCPU 107 determines that the electronic device 200 is not in a stateenabling to receive the power from the external apparatus 400 (NO instep S403), the process proceeds from step S403 to step S406.

In step S404, the CPU 107 performs wireless communication conforming tothe NFC standard to transmit a second command to the electronic device200. The second command is used for instructing the electronic device200 so as to select the external apparatus 400 as an apparatus whichsupplies the power to the electronic device 200.

Upon reception of the second command from the power supply apparatus100, the CPU 205 controls the first switching unit 212 so that the poweris supplied to the regulator 209 from the external apparatus 400. Inthis case, the CPU 205 performs control so that the switch 501 is set toOFF and the switch 502 is set to ON. In this case, the externalapparatus 400 supplies the power to the regulator 209, and the regulator209 supplies to the electronic device 200 the power supplied from theexternal apparatus 400. When the battery 211 is not fully charged, thecharging control unit 210 charges the battery 211 with the powersupplied from the external apparatus 400 via the regulator 209.

When the first switching unit 212 is controlled so that the powersupplied from the external apparatus 400 is supplied to the regulator209, the electronic device 200 transmits response data corresponding tothe second command to the power supply apparatus 100. When the secondcommand is transmitted to the electronic device 200, the processproceeds from step S404 to step S405.

In step S405, the CPU 107 controls the oscillator 102, the powergeneration unit 103, and the matching circuit 104 not to output thepower via the power transmitting antenna 106. In this case, the processin the flowchart in FIG. 4 is ended.

In step S406, the CPU 107 performs wireless communication conforming tothe NFC standard to transmit a third command to the electronic device200. The third command is used for instructing the electronic device 200so as to select the power supply apparatus 100 as an apparatus whichsupplies the power to the electronic device 200.

Upon reception of the third command from the power supply apparatus 100,the CPU 205 controls the first switching unit 212 so that the powerreceived from the power supply apparatus 100 via the power receivingantenna 201 is supplied to the regulator 209. In this case, the CPU 205performs control to turn ON the switch 501 and turn OFF the switch 502.In this case, the power received by the electronic device 200 from thepower supply apparatus 100 is supplied to the regulator 209. Theregulator 209 supplies power to the electronic device 200 from the powersupply apparatus 100. If the battery 211 is not fully charged, thecharging control unit 210 charges the battery 211 with the powersupplied from the power supply apparatus 100 via the regulator 209.

When the first switching unit 212 is controlled so that the power issupplied to the regulator 209 from the power supply apparatus 100, theelectronic device 200 transmits response data corresponding to the thirdcommand to the power supply apparatus 100. When the third command istransmitted to the electronic device 200, the process proceeds from stepS406 to step S407.

In step S407, the CPU 107 controls the oscillator 102, the powergeneration unit 103, and the matching circuit 104 to output the secondpower via the power transmitting antenna 106. Then, the process proceedsfrom step S407 to step S408.

In step S408, the CPU 107 detects whether a change of the VSWR is equalto or larger than the predetermined value A. When the CPU 107 determinesthat a change of the VSWR is equal to or larger than the predeterminedvalue A (YES in step S408), the process proceeds from step S408 to stepS409. When the CPU 107 determines that a change of the VSWR is less thanthe predetermined value A (NO in step S408), the process proceeds fromstep S408 to step S411.

In step S409, the CPU 107 detects whether one or more electronic devicesexist within the predetermined range. When one or more electronicdevices exist within the predetermined range (YES in step S409), theprocess proceeds from step S409 to step S410. When one or moreelectronic devices are not exist within the predetermined range (NO instep S409), the CPU 107 determines that no electronic device existswithin the predetermined range of distance. In this case (NO in stepS409), the process proceeds from step S409 to step S405.

In step S410, similar to the process in step S405, the CPU 107 controlsthe oscillator 102, the power generation unit 103, and the matchingcircuit 104 not to output the power via the power transmitting antenna106. Then, the process returns from step S410 to step S402.

In step S411, the CPU 107 determines whether power supply is to beended. For example, in step S406, if the CPU 107 detects that noelectronic device which the third command was transmitted from the powersupply apparatus 100 exists within the predetermined range to, the CPU107 determines that power supply is to be ended.

For example, in step S406, if the CPU 107 detects that chargingperformed by the electronic device to which the third command wastransmitted from the power supply apparatus 100 is stopped, the CPU 107determines that power supply is to be ended. When the CPU 107 determinesthat power supply is to be ended (YES in step S411), the processproceeds from step S411 to step S405. When the CPU 107 determines thatpower supply is not to be ended (NO in step S411), the process returnsfrom step S411 to step S408. When the CPU 107 determines that powersupply is not to be ended (NO in step S411), the power supply apparatus100 continuously supplies the power.

When the CPU 107 determines that a plurality of electronic devices existwithin the predetermined range (YES in step S402), then in step S404,the CPU 107 transmits the second command to the plurality of electronicdevices existing within the predetermined range.

Thus, the power supply apparatus 100 according to the first exemplaryembodiment selects an apparatus capable of suitably supplying the powerto the electronic device 200.

When a plurality of electronic devices exists within the predeterminedrange (YES in step S402), the power supply apparatus 100 selects theexternal apparatus 400. When a plurality of electronic devices existswithin the predetermined range, the power supply apparatus 100 suppliesthe power in parallel to the plurality of electronic devices. In thiscase, the power supplied from the power supply apparatus 100 to eachelectronic device is lower than that in a case where the power supplyapparatus 100 supplies the power to one electronic device. This meansthat the electronic device 200 cannot efficiently receive the power fromthe power supply apparatus 100. Therefore, in a case where a pluralityof electronic devices exists within the predetermined range, the powersupply apparatus 100 enables the plurality of electronic devices toreceive the power from the external apparatus 400.

When the electronic device 200 can receive the power from the externalapparatus 400 (YES in step S403), the power supply apparatus 100 selectsthe external apparatus 400. When the power supply apparatus 100 suppliesthe power to the electronic device 200, the power received by theelectronic device 200 from the power supply apparatus 100 is affected bya state of the electronic device 200 and an operating state of the powersupply apparatus 100. Thus, the external apparatus 400 is sometimes ableto supply to the electronic device 200 more stable power than the powersupply apparatus 100. Therefore, when the electronic device 200 canreceive the power from the external apparatus 400 (YES in step S403),the power supply apparatus 100 enables the electronic device 200 toreceive the power from the external apparatus 400.

When the electronic device 200 cannot receive the power from theexternal apparatus 400 (NO in step S403), the power supply apparatus 100selects the power supply apparatus 100. In this case, the power supplyapparatus 100 enables the electronic device 200 to receive the powerfrom the power supply apparatus 100.

When a change of the VSWR is equal to or larger than the predeterminedvalue A (YES in step S408), the power supply apparatus 100 detectswhether one or more electronic devices exists within the predeterminedrange. When a change of the VSWR is equal to or larger than thepredetermined value A (YES in step S408), the number of the electronicdevices existing within the predetermined range may have changed. Inthis case, when one or more electronic devices exists within thepredetermined range (YES in step S409), the CPU 107 once stops output ofthe power and then reselects either the power supply apparatus 100 orthe external apparatus 400. Therefore, according to a change of thenumber of electronic devices existing within the predetermined range,the power supply apparatus 100 can reselect an apparatus capable ofsuitably supplying the power to the electronic device 200.

Therefore, the power supply apparatus 100 can select an apparatuscapable of supplying suitable power to the electronic device 200.

A second exemplary embodiment according to the present invention will bedescribed below. In the second exemplary embodiment, for similarconfigurations, processes, and operations to the first exemplaryembodiment, redundant description will be omitted.

(Selection Process)

A selection process performed by the power supply apparatus 100according to the second exemplary embodiment will be described belowwith reference to the flowchart in FIG. 5. The selection process in FIG.5 can be implemented when the CPU 107 executes a computer program storedin the ROM 108.

For the process similar to the selection process described in the firstexemplary embodiment, redundant description will be omitted. Onlydifferent processes will be described below.

In step S501 and steps S505 to S512, the processes common to step S401and steps S404 to S411 are performed, thus redundant description will beomitted.

In step S502, the CPU 107 determines whether a plurality of electronicdevices exist within the predetermined range. When the CPU 107determines that a plurality of electronic devices exists within thepredetermined range (YES in step S502), the process proceeds from stepS502 to step S513. When the CPU 107 determines that a plurality ofelectronic devices does not exist within the predetermined range (NO instep S502), the process proceeds from step S502 to step S503.

In step S503, the CPU 107 determines whether the electronic device 200is in a state enabling to for receive the power from the externalapparatus 400. When the CPU 107 determines that the electronic device200 is in a state enabling to for receive the power from the externalapparatus 400 (YES in step S503), the process proceeds from step S503 tostep S504. When the CPU 107 determines that the electronic device 200 isnot in a state enabling to receive the power from the external apparatus400 (NO in step S503), the process proceeds from step S503 to step S507.

In step S504, the CPU 107 determines which of the power supply apparatus100 and the external apparatus 400 can supply larger power to theelectronic device 200.

In this case, the CPU 107 performs wireless communication conforming tothe NFC standard to transmit a fourth command to the electronic device200. The fourth command is used for requesting information indicatingthe power received by the electronic device 200 from the power supplyapparatus 100. Upon reception of the fourth command from the powersupply apparatus 100, the electronic device 200 detects first powerinformation indicating the power received by the electronic device 200from the power supply apparatus 100, using the current information andthe voltage information supplied from the current and voltage detectionunit 208. In this case, the electronic device 200 transmits responsedata including the first power information to the power supply apparatus100.

The CPU 107 performs wireless communication conforming to the NFCstandard to transmit a fifth command to the electronic device 200. Thefifth command is used for requesting information indicating the powersupplied from the external apparatus 400 to the electronic device 200.Upon reception of the fifth command from the power supply apparatus 100,the electronic device 200 detects second power information indicatingthe power supplied from the external apparatus 400 to the electronicdevice 200, using the information indicating the current supplied fromthe current limiting unit 215. In this case, the electronic device 200transmits response data including the second power information to thepower supply apparatus 100.

When the first power information and the second power information areobtained from the electronic device 200, the CPU 107 compares the powerreceived by the electronic device 200 from the power supply apparatus100 with the power supplied from the external apparatus 400 to theelectronic device 200, using the first power information and the secondpower information.

When the CPU 107 determines that the power received by the electronicdevice 200 from the power supply apparatus 100 is larger than the powersupplied from the external apparatus 400 to the electronic device 200(YES in step S504), the process proceeds from step S504 to step S507.When the CPU 107 determines that the power received by the electronicdevice 200 from the power supply apparatus 100 is not larger than thepower supplied from the external apparatus 400 to the electronic device200 (NO in step S504), the process proceeds from step S504 to step S505.

In step S513, the CPU 107 performs an exception process described below.After completion of the exception process, the process in the flowchartin FIG. 5 is ended.

Although, in step S504, the CPU 107 compares the power received by theelectronic device 200 from the power supply apparatus 100 with the powersupplied from the external apparatus 400 to the electronic device 200,the process is not limited thereto. For example, in step S504, the CPU107 may compare the power output from the power transmitting antenna106, instead of the power received by the electronic device 200 from thepower supply apparatus 100, with the power supplied from the externalapparatus 400 to the electronic device 200.

The exception process in step S513 performed in the selection process inFIG. 5 according to the second exemplary embodiment will be describedbelow with reference to a flowchart in FIG. 6. The exception processillustrated in FIG. 6 can be implemented when the CPU 107 executes acomputer program stored in the ROM 108.

The CPU 107 performs the exception process in step S513 when it isdetermined that a plurality of electronic devices exists within thepredetermined range (YES in step S502). The exception process in stepS513 is performed in a case where the electronic device 200 and anelectronic device 500 exist within the predetermined range, asillustrated in FIG. 7.

The exception process in a power supply system as illustrated in FIG. 7will be described below as an example. In this case, it is assumed thatthe electronic device 500 has a similar configuration to the electronicdevice 200. Further, the electronic device 500 may be connected to theexternal apparatus 400 via a cable 600, as illustrated in FIG. 7. Thecable 600 also has a similar configuration to the cable 300. Further,the electronic device 500 is supplied power from the external apparatus400 via the cable 600. If the CPU 107 determines that the electronicdevice 200 and the electronic device 500 exist within the predeterminedrange, the CPU 107 performs a process of step S601.

In step S601, the CPU 107 determines whether the electronic device 200and the electronic device 500 are in a state enabling to receive thepower from the external apparatus 400.

When the CPU 107 determines that the electronic device 200 and theelectronic device 500 are in a state enabling to receive the power fromthe external apparatus 400 (YES in step S601), the process proceeds fromstep S601 to step S602. When the CPU 107 determines that the electronicdevice 200 and the electronic device 500 are not in a state enabling toreceive the power from the external apparatus 400 (NO in step S601), theCPU 107 determines that at least one of the electronic device 200 andthe electronic devices 500 cannot receive power from the externalapparatus 400. In this case, (NO in step S601), the process proceedsfrom step S601 to step S603.

In step S602, the CPU 107 performs wireless communication conforming tothe NFC standard to transmit the second command to the electronic device200 and the electronic device 500. When the electronic device 200receives the second command from the power supply apparatus 100, theelectronic device 200 supplies power to the electronic device 200 fromthe external apparatus 400. Further, the electronic device 200 preventspower from supplying from the power supply apparatus 100 to theelectronic device 200. When the electronic device 500 receives thesecond command from the power supply apparatus 100, the electronicdevice 500 supplies to the electronic device 500 from the externalapparatus 400. Further, the electronic device 500 and prevents powerfrom supplying from the power supply apparatus 100 to the electronicdevice 500. In this case, the process proceeds from step S602 to stepS506.

In step S603, the CPU 107 determines whether an apparatus which cannotreceive the power from the external apparatus 400 is either theelectronic device 200 or the electronic devices 500. When the CPU 107determines that the apparatus which cannot receive the power from theexternal apparatus 400 is either the electronic device 200 or theelectronic devices 500 (YES in step S603), the process proceeds fromstep S603 to step S604. When the CPU 107 determines that the apparatuswhich cannot receive the power from the external apparatus 400 is noteither the electronic device 200 or the electronic devices 500 (NO instep S603), the electronic device 200 and the electronic device 500cannot receive the power from the external apparatus 400. In this case,(NO in step S603), the process proceeds from step S603 to step S606.

In step S604, the CPU 107 performs wireless communication conforming tothe NFC standard to transmit the third command to an electronic devicedetermined to be unable to receive the power from the external apparatus400.

For example, when the electronic device 200 receives the third commandfrom the power supply apparatus 100, the electronic device 200 preventspower from supplying from the external apparatus 400 to the electronicdevice 200. Further, the electronic device 200 supplies power to theelectronic device 200 from the power supply apparatus 100. Further, forexample, when the electronic device 500 receives the third command fromthe power supply apparatus 100, the electronic device 500 prevents powerfrom supplying from the external apparatus 400 to the electronic device500. Further, the electronic device 500 supplies power to the electronicdevice 500 from the power supply apparatus 100. In this case, theprocess proceeds from step S604 to step S605.

In step S605, the CPU 107 performs wireless communication conforming tothe NFC standard to transmit the second command to an electronic deviceother than the electronic device to which the third command wastransmitted in step S604. In this case, the process proceeds from stepS605 to step S508.

In step S606, the CPU 107 compares an efficiency of power transmissionfrom the power supply apparatus 100 to the electronic device 200 with anefficiency of power transmission from the power supply apparatus 100 tothe electronic device 500.

The CPU 107 detects first efficiency information indicating theefficiency of power transmission from the power supply apparatus 100 tothe electronic device 200 and second efficiency information indicatingthe efficiency of power transmission from the power supply apparatus 100to the electronic device 500. The CPU 107 compares the first efficiencyinformation with the second efficiency information to determine which ofthe electronic device 200 and the electronic device 500 can efficientlyreceive the power from the power supply apparatus 100. In this case, theprocess proceeds from step S606 to step S607.

In step S607, the CPU 107 performs wireless communication conforming tothe NFC standard to transmit the third command to an electronic devicedetermined to be able to efficiently receive the power from the powersupply apparatus 100.

When the efficiency of power transmission from the power supplyapparatus 100 to the electronic device 200 is higher than the efficiencyof power transmission from the power supply apparatus 100 to theelectronic device 500, the CPU 107 transmits the third command to theelectronic device 200. Otherwise, when the efficiency of powertransmission from the power supply apparatus 100 to the electronicdevice 200 is lower than the efficiency of power transmission from thepower supply apparatus 100 to the electronic device 500, the CPU 107transmits the third command to the electronic device 500.

When the efficiency of power transmission from the power supplyapparatus 100 to the electronic device 200 is equal to the efficiency ofpower transmission from the power supply apparatus 100 to the electronicdevice 500, the CPU 107 may transmit the third command to an apparatusfirst determined to exist within the predetermined range. Further, whenthe efficiency of power transmission from the power supply apparatus 100to the electronic device 200 is equal to the efficiency of powertransmission from the power supply apparatus 100 to the electronicdevice 500, the CPU 107 may transmit the third command to an apparatushaving large power consumption. Further, when the efficiency of powertransmission from the power supply apparatus 100 to the electronicdevice 200 is equal to the efficiency of power transmission from thepower supply apparatus 100 to the electronic device 500, the CPU 107 maytransmit the third command to an apparatus having smaller remainingcapacity of the battery. In this case, the process proceeds from stepS607 to step S608.

In step S608, the CPU 107 performs wireless communication conforming tothe NFC standard to transmit the second command to an electronic deviceother than the electronic device to which the third command wastransmitted in step S607. In this case, the process proceeds from stepS608 to step S508.

Thus, based on the result of the comparison between the power receivedby the electronic device 200 from the power supply apparatus 100 and thepower supplied from the external apparatus 400 to the electronic device200, the power supply apparatus 100 according to the second exemplaryembodiment selects an apparatus capable of suitably supplying the powerto the electronic device 200.

When the power received by the electronic device 200 from the powersupply apparatus 100 is larger than the power supplied from the externalapparatus 400 to the electronic device 200 (YES in step S504), the CPU107 selects the power supply apparatus 100. In this case, the powersupply apparatus 100 can efficiently supply the power to the electronicdevice 200.

When the power received by the electronic device 200 from the powersupply apparatus 100 is not larger than the power supplied from theexternal apparatus 400 to the electronic device 200 (NO in step S504),the CPU 107 selects the external apparatus 400. In this case, the powersupply apparatus 100 enables efficient a supply of power from theexternal apparatus 400 to the electronic device 200. Further, in thiscase, if the power received by the electronic device 200 from the powersupply apparatus 100 is equal to the power supplied from the externalapparatus 400 to the electronic device 200, the CPU 107 selects theexternal apparatus 400. This is because it is likely that the externalapparatus 400 can supply more stable power to the electronic device 200than the power supply apparatus 100.

According to the second exemplary embodiment, when a plurality ofelectronic devices exists within the predetermined range (YES in stepS502), the CPU 107 determines whether each electronic device is in astate enabling to receive the power from the external apparatus 400.Further, based on the result of the determination, the CPU 107 selectsan apparatus capable of suitably supplying the power to each electronicdevice.

Therefore, if a plurality of electronic devices exists within thepredetermined range of distance, the power supply apparatus 100 canselect an apparatus capable of suitably supplying the power for eachelectronic device.

With the power supply apparatus 100 according to the second exemplaryembodiment, portions common to the processes and configurationsdescribed in the first exemplary embodiment have similar effects to thefirst exemplary embodiment.

Although the power supplied from the external apparatus 400 via thecable 600 is supplied to the electronic device 500, the electronicdevice 500 may be supplied power from an apparatus other than theexternal apparatus 400 via the cable 600.

A third exemplary embodiment according to the present invention will bedescribed below. In the third exemplary embodiment, for similarconfigurations, processes, and operations to the first and secondexemplary embodiments, redundant description will be omitted.

The electronic device 200 according to the third exemplary embodimentincludes a first switching unit 212 as illustrated in FIG. 8. The firstswitching unit 212 according to the third exemplary embodiment includesa diode 801, a diode 802, and a resistor 803.

Referring to FIG. 8, the rectifying and smoothing circuit 203 and theregulator 209 are connected via the diode 801, and the current limitingunit 215 and the regulator 209 are connected via the diode 802.

The resistor 803 is connected between the diode 802 and the CPU 205.When the power is supplied from the external apparatus 400 to theelectronic device 200 via the connector 213, a voltage is generated atthe resistor 803.

The CPU 205 can detect whether the power is supplied from the externalapparatus 400 by detecting the voltage of the resistor 803. Whicheverlarger the power supplied from the power supply apparatus 100 to theelectronic device 200 or the power supplied from the external apparatus400 to the electronic device 200 is supplied to the regulator 209.

The CPU 205 detects a voltage level supplied from the power supplyapparatus 100 using the voltage information supplied from the currentand voltage detection unit 208. The CPU 205 detects a voltage levelsupplied from the external apparatus 400 using the voltage informationobtained by detecting the voltage of the resistor 803. The voltage levelsupplied from the power supply apparatus 100 is referred to as a firstvoltage level, and the voltage level supplied from the externalapparatus 400 is referred to as a second voltage level.

According to the third exemplary embodiment, the CPU 107 performs theselection process in FIG. 5. When performing the process in step S504,the CPU 107 may, by comparing the first voltage level with the secondvoltage level, determine which of the power supply apparatus 100 and theexternal apparatus 400 can supply larger power to the electronic device200.

In this case, the CPU 107 performs wireless communication conforming tothe NFC standard to transmit to the electronic device 200 a sixthcommand for requesting the first voltage level. Upon reception of thesixth command from the power supply apparatus 100, the electronic device200 detects the first voltage level. The electronic device 200 transmitsresponse data including the first voltage level to the power supplyapparatus 100.

The CPU 107 performs wireless communication conforming to the NFCstandard to transmit to the electronic device 200 for requesting thesecond voltage level. Upon reception of the seventh command from thepower supply apparatus 100, the electronic device 200 detects the secondvoltage level. The electronic device 200 transmits response dataincluding the second voltage level to the power supply apparatus 100.

When the first voltage level and the second voltage level are obtainedfrom the electronic device 200, the CPU 107 compares the first voltagelevel with the second voltage level. When the CPU 107 determines thatthe first voltage level is larger than the second voltage level (YES instep S504), the process proceeds from step S504 to step S507. When theCPU 107 determines that the first voltage level is not larger than thesecond voltage level (NO in step S504), the process proceeds from stepS504 to step S505.

With the power supply apparatus 100 according to the third exemplaryembodiment, portions common to the processes and configurationsdescribed in the first and second exemplary embodiments have similareffects to the first and second exemplary embodiments.

Although, according to the first, second, and third exemplaryembodiments, the power supply apparatus 100 performs wirelesscommunication conforming to the NFC standard, the process is not limitedthereto. For example, the power supply apparatus 100 may performwireless communication conforming to the International Organization forStandardization/International Electrotechnical Commission (ISO/IEC)18092 standard, such as the Radio Frequency Identification (RFID)standard or the Transfer Jet (registered trademark) standard. Further,for example, the power supply apparatus 100 may perform wirelesscommunication conforming to the Mikron Fare-collection System (MIFARE)(registered trademark) standard or the FeliCa (registered trademark)standard.

Although, according to the first, second, and third exemplaryembodiments, the electronic device 200 can receive the power from theexternal apparatus 400 via the cable 300, the process is not limitedthereto. For example, instead of the external apparatus 400 beingconnected to the electronic device 200 via the cable 300, a device whichoutputs the DC power from a commercial power supply may be connected tothe electronic device 200. The device which outputs the DC power from acommercial power supply is, for example, an AC adapter. The cable 300may conform to a standard other than the USB standard. Even in a casewhere an AC adapter is connected to the electronic device 200, the powersupply apparatus 100 may perform the selection process in FIG. 4 and theselection process in FIG. 5 similar to a case where the externalapparatus 400 is connected to the electronic device 200 via the cable300.

According to the first, second, and third exemplary embodiments, thepower supply apparatus 100 selects either the power supply apparatus 100or the external apparatus 400 as an apparatus capable of suitablysupplying the power to the electronic device 200.

Subsequently, when the CPU 107 detects that the state of connectionbetween the electronic device 200 and the external apparatus 400 haschanged, the power supply apparatus 100 may select again an apparatuscapable of suitably supplying the power to the electronic device 200. Inthis case, for example, when the external apparatus 400 is selected bythe power supply apparatus 100 as an apparatus which supplies the powerto the electronic device 200 and then the electronic device 200 and theexternal apparatus 400 are disconnected, the power supply apparatus 100may select again an apparatus capable of suitably supplying the power tothe electronic device 200, by performing again the selection process inFIG. 4 or the selection process in FIG. 5.

Further, for example, when the power supply apparatus 100 is selected bythe power supply apparatus 100 as an apparatus which supplies the powerto the electronic device 200 and then the electronic device 200 and theexternal apparatus 400 are connected, the power supply apparatus 100 mayselect again an apparatus capable of suitably supplying the power to theelectronic device 200, by performing again the selection process in FIG.4 or the selection process in FIG. 5.

Further, when the power supply apparatus 100 detects that the powersupplied from the external apparatus 400 to the electronic device 200has changed, the power supply apparatus 100 may select again anapparatus capable of suitably supplying the power to the electronicdevice 200. In this case, for example, when the external apparatus 400is selected by the power supply apparatus 100 as an apparatus whichsupplies the power to the electronic device 200 and then the powersupplied from the external apparatus 400 to the electronic device 200decreases, the power supply apparatus 100 may select again an apparatuscapable of suitably supplying the power to the electronic device 200, byperforming again the selection process in FIG. 4 or the selectionprocess in FIG. 5.

Further, for example, when the power supply apparatus 100 is selected bythe power supply apparatus 100 as an apparatus which supplies the powerto the electronic device 200 and then the power supplied from theexternal apparatus 400 to the electronic device 200 increases, the powersupply apparatus 100 may select again an apparatus capable of suitablysupplying the power to the electronic device 200, by performing againthe selection process in FIG. 4 or the selection process in FIG. 5.

If the power supply apparatus 100 stops power output in the process instep S405 or S506, the power supply apparatus 100 may continue wirelesscommunication conforming to the NFC standard with the electronic device200.

Aspects of the present invention can also be realized by a computer of asystem or apparatus (or devices such as a CPU or an MPU) that reads outand executes a program recorded on a memory device to perform thefunctions of the above-described embodiments, and by a method, the stepsof which are performed by a computer of a system or apparatus by, forexample, reading out and executing a program recorded on a memory deviceto perform the functions of the above-described embodiments. For thispurpose, the program is provided to the computer for example via anetwork or from a recording medium of various types serving as thememory device (e.g., computer-readable medium).

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures, and functions.

What is claimed is:
 1. A wireless power system including a power supplydevice and a power receiving device, the power supply system comprising:a power receiving unit that receives power wirelessly from the powersupply device; a connection unit that connects between the powerreceiving device and an external device, the external device beingdifferent from the power supply device; a control unit that controls thepower receiving device to receive power from the external device in acase where the power receiving device is in a state that enables thepower receiving device to receive power from the external device througha connection between the power receiving device and the external device,the external device being different from the power supply device, and toreceive power from the power supply device in a case where the powerreceiving device is not in the state that enables the power receivingdevice to receive power from the external device.
 2. The wireless powersystem according to claim 1, wherein the control unit that transmits viathe communication unit first data to the power receiving device if thepower receiving device and the external device are connected.
 3. Thewireless power system according to claim 2, wherein the control unitcontinues to communicate with the power receiving device after the firstdata is transmitted to the power receiving device.
 4. The wireless powersystem according to claim 1, wherein the control unit controls thecommunication unit to transmit second data to the power receiving deviceif the power receiving device and the external device are not connected.5. The wireless power system according to claim 1, wherein the controlunit controls the power supply unit to limit power for supplying to thepower receiving device if the power receiving device and the externaldevice are connected.
 6. The wireless power system according to claim 1,wherein the control unit controls the communication unit to transmitpredetermined data to the power receiving device based on a first leveland a second level if the power receiving device and the external deviceare connected, and wherein the first level indicates a level of powersupplied from the power supply device to the power receiving device, andthe second level indicates a level of power supplied from the externaldevice to the power receiving device.
 7. The wireless power systemaccording to claim 6, wherein the control unit controls thecommunication unit to transmit second data to the power receiving deviceif the first level is higher than the second level.
 8. The wirelesspower system according to claim 6, wherein the control unit controls thecommunication unit to transmit first data to the power receiving deviceif the first level is not higher than the second level.
 9. The wirelesspower system according to claim 1, wherein the control unit controls thepower supply unit to supply predetermined power to the power receivingdevice if the power receiving device and the external device are notconnected, and the predetermined power is used for charging a battery.10. The wireless power system according to claim 1, further comprising adetection unit that detects one or more power receiving devices,wherein, if the detection unit detects a plurality of power receivingdevices, the control unit controls the communication unit to transmitcommand to the plurality of power receiving devices, and wherein thecommand is used for controlling not to receive power from the powersupply device.
 11. The wireless power system according to claim 1,further comprising a detection unit that detects one or more powerreceiving devices, and wherein the control unit performs a process forcontrolling the communication unit to transmit predetermined data if anumber of power receiving devices detected by the detection unit ischanged.
 12. The wireless power system according to claim 1, wherein theexternal device is different from a battery.
 13. The wireless powersystem according to claim 1, wherein the external device includes an ACadapter.
 14. The wireless power system according to claim 1, wherein theexternal device includes a device that can supply power to the powerreceiving device based on Universal Serial Bus (USB).
 15. The wirelesspower system according to claim 1, wherein the control unit thatcompares a level of power received from the power supply device to alevel of power supplied by the external apparatus, wherein in responseto the power receiving device being in a state that enables the powerreceiving device to receive power from the external device and the levelof power received from the power supply device being less than the levelof power supplied by the external apparatus, the control unit selectsthe external apparatus to supply power to the power receiving device,and wherein in response to either the power receiving device not beingin a state that enables the power receiving device to receive power fromthe external device or the level of power received from the power supplydevice being greater than the level of power supplied by the externalapparatus, the control unit selects the external apparatus to supplypower to the power receiving device.
 16. A method for controlling awireless power system including a power supply device and a powerreceiving device, the method comprising: wirelessly supplying power;communicating with the power receiving device different from the powersupply device; and transmitting predetermined data to the powerreceiving device based on whether or not the power receiving device isin a state that enables the power receiving device to receive power froman external device through a connection between the power receivingdevice and the external device, the external device being different fromthe power supply device, wherein the predetermined data includes one offirst data and second data, the first data is used for causing the powerreceiving device to receive power from the external device, and thesecond data is used for causing the power receiving device to receivepower from the power supply device, and wherein the external deviceincludes a device for supplying power to the power receiving device. 17.A recording medium recording a program for causing a computer to executea method for controlling a wireless power system including a powersupply device and a power receiving device, the method comprising:wirelessly supplying power; communicating with a power receiving devicedifferent from the power supply device; and transmitting predetermineddata to the power receiving device based on whether or not the powerreceiving device is in a state that enables the power receiving deviceto receive power from an external device through a connection betweenthe power receiving device and the external device, the external devicebeing different from the power supply device, wherein the predetermineddata includes one of first data and second data, the first data is usedfor causing the power receiving device to receive power from theexternal device, and the second data is used for causing the powerreceiving device to receive power from the power supply device, andwherein the external device includes a device for supplying power to thepower receiving device.